1. Field of the Invention
This invention generally relates to a linear motion guide unit and in particular to a retainer for use in such a linear motion guide unit which is particularly suitable for use as a guide unit of a magnetic head assembly in various measuring apparatuses and computer related apparatuses.
2. Description of the Prior Art
A linear motion guide unit is well known and it typically includes an elongated rail, a slider slidably mounted on the rail, a plurality of rolling members interposed between the rail and the slider and a retainer also interposed between the rail and the slider for retaining the rolling members in position during a relative sliding motion between the rail and the slider. Such a linear motion guide unit may be used in various applications, and a compact and light-weight linear motion guide unit particularly suitable for use as a guide unit in a magnetic head assembly in a computer related apparatus is disclosed in the Japanese Utility Model Post-examination Publication No. 62-35943 and schematically shown in FIG. 4 here.
As shown in FIG. 4, such a linear motion guide unit generally includes an elongated rail, a table or slider A slidably mounted on the rail, a plurality of rolling members or balls in the illustrated example interposed between the rail and the slider A, and a retainer C for retaining the balls in position. In such a structure, in order to prevent the retainer C from slipping away from each end of the slider A or the rail, a stopper B is typically fixedly attached to the slider A at each end thereof. Thus, the retainer C is prevented from slipping away since its each end surface D comes into contact with an associated stopper B at its extreme end of the stroke, so that the retainer C may be always kept in a space defined between the rail and the slider A so as to keep the balls in position.
Because of the provision of such stoppers B at both ends of the slider A, the stroke of the table A relative to the rail is shortened by twice the width of the stopper B since the stopper B is provided on both ends of the slider A. Put it another way, the effective stroke distance becomes shorter as compared with the actual length of the slider A and thus there is a limit in reducing the overall size of the entire assembly.